1. Field of the Invention
The present invention relates generally to a device including mutually movable housing portions and locking means for locking the housing portions to each other. More particularly, the present invention relates to a structure for releasably locking a covering element in a closed position on a housing. The present invention may be considered as a structure for locking a covering element attached to a housing of a portable electrical unit, such as a hand-held terminal unit, a portable telephone, a video camera, a notebook-size personal computer, and so forth, to selectively open and close an opening defined in the housing.
2. Description of the Related Art
Various locking structures have been known in the art, which can releasably lock a covering element or lid in a closed position for closing an opening, such as an opening of a battery receptacle, a memory-card receptacle, and so on, defined in a housing of a portable electrical unit, such as a hand-held terminal unit, a portable telephone, a video camera, a notebook-size personal computer, and so forth. For example, it is known to provide a resilient hook, made of resin, along an edge portion of the covering element. The resilient hook can be engaged in a snap-fit manner with an inner shoulder formed along a peripheral edge of the opening defined in the housing when the covering element is attached to close the opening, and thus can lock the covering element in a closed position.
Another conventional locking structure is known as a shiftable member rotatably or slidably supported on the covering element to be able to move between locked and unlocked positions. The shiftable member is normally provided at one end thereof with a knob accessibly arranged outside the covering element, and at the other end thereof with an engagement piece disposed inside the covering element. The engagement piece can be engaged with an inner shoulder formed along a peripheral edge of the opening defined in the housing when the covering element is located to close the opening and the shiftable member is shifted into the locked position, and thus can lock the covering element in a closed position.
The above-mentioned conventional locking structures for the covering elements have several problems, as follows. Since the stability and reliability of the locking function of the resilient-hook locking structure depend only on the resilient property of the hook, the resilient-hook locking structure is relatively easily released or disengaged from the peripheral-edge inner shoulder of the opening when the covering element and/or the housing is subjected to vibration or shock.
Also, the shiftable-member locking structure increases the number of parts, and generally makes it difficult to reduce the size and/or weight of the portable electrical unit. Further, in the shiftable-member locking structure, the operation for shifting the shiftable member is usually troublesome. Moreover, since the shiftable member cannot be fully shifted into the locked position until the covering element is completely located in the closed position, it is necessary to confirm that the shiftable member has certainly or correctly locked the covering element in the closed position, to eliminate inadvertently opening or half-opening the covering element.